Graphene Oxide Covered WO₃ Nanosheet Arrays as Photoelectrode for Photoelectrochemical Detection of Trace H₂O₂

Accurate detection of trace hydrogen peroxide (H2O2) by the anode photoelectrochemical (PEC) method is highly attractive in the modern chemical industry. However, the sluggish hole migration kinetics in photocatalysts are severely unfavorable for hole enrichment on the photoanodic surface, limiting the method's sensitivity and detection limit in practical applications. Herein, we proposed graphene oxide (GO) with high conductivity as cocatalyst to capture and aggregate hole tactics for tackling this formidable mission. As a proof of concept, GO covered tungsten trioxide (WO3) nanosheet arrays as photoelectrode were selected and cast as a prototype. The as-synthesized WO3 nanosheet only showed a thickness of 120–140 nm. Optical and structural characterizations demonstrate that GO was validated to accelerate the oxidation of H2O2 to O2 rather than •OH by improving the hole density on the surface of GO/WO3 and reducing the overpotential of H2O2 decomposition. Subsequently, it helps to boost the oxidation current of H2O2 on the GO/WO3 photoanode (24.7 μA cm−2 in 2 mM H2O2) at a lower potential of 0.7 V vs RHE. As a result, the lower minimum detection limit and sensitivity of H2O2 detection by the GO/WO3 photoanode are up to 0.1 mM and 8.14 μA cm−2 mM−1, respectively, which are 0.25 (0.4 mM) and 2.91 (2.79 μA cm−2 mM−1) times sensitive than that of WO3 photoanode. This work affords a strategy to boost the sensitivity and detection limit of trace H2O2 detection, which may have applications in biological analysis and the early detection of diseases.